Apparatus for cleaning submerged surfaces

ABSTRACT

A liquid under pressure flows through a conduit to an inlet of a jet pump means from which issues a high velocity stream of liquid. An area of pressure lower than ambient pressure is established in the high velocity stream and this is communicated through a passageway to an inner face of a compressible resilient pad which is to be disposed against the submerged surface. A pressure differential exists between the ambient liquid on the outer side of the pad and the liquid flowing between the inner surface of the pad and the submerged surface and this pressure differential urges the compressible pad toward the submerged surface to conform to the contour thereof and results in a thin high velocity film of liquid flow across the submerged surface to clean the same. Rubbing contacts between the submerged surface and asperities on the surface of the pad serves to augment the cleaning action of the liquid flow. The resilient pad may also be somewhat porous thus allowing the flow of some liquid directly from the peripheral areas of the pad to the inlet of the jet pump thus tending to increase the surface flow velocity in these peripheral areas.

United States Patent [1 1 Brower [451 Jan. 2, 1973 [54] APPARATUS FOR CLEANING SUBMERGED SURFACES [7 5] Inventor: David F. Brower, San Diego, Calif.

[73] Assignee: Peltec Corporation,

Calif.

[22] Filed: Aug. 30, 1971 [211 App]. No.: 175,820

San Diego,

[52] U.S. Cl. ..15/1.7, 15/409, 114/222, 401/13 [51] Int. Cl. ..E04h 3/20 [58] Field of Search ..l5/1.7, 210, 246.5, 409 X; 114/222 X; 401/13; 134/21 l/l963 Mullinix et a1 .15/l.7 X 5/1966 Crawford ..l14/222 Primary ExaminerEdward L. Roberts Attorney-William E. Anderson et al.

[57 ABSTRACT A liquid under pressure flows through a conduit to an inlet of a jet pump means from which issues a high velocity stream of liquid. An area of pressure lower than ambient pressure is established in the high velocity stream and this is communicated through a passageway to an inner face of a compressible resilient pad which is to be disposed against the submerged surface. A pressure differential exists between the ambient liquid on the outer side of the pad and the liquid flowing between the inner surface of the pad and the submerged surface and this pressure differential urges the compressible pad toward the submerged surface to conform to the contour thereof and results in a thin high velocity film of liquid flow across the submerged surface to clean the same. Rubbing contacts between the submerged surface and asperities on the surface of the pad serves to augment the cleaning action of the liquid flow. The resilient pad may also be somewhat porous thus allowing the flow of some liquid directly from the peripheral areas of the pad to the inlet of the jet pump thus tending to increase the surface flow velocity in these peripheral areas.

10 Claims, 5 Drawing Figures 'PATENTEDJANZ ms K. 3,107.73?

'SHEET 2 OF 2 FIGS APPARATUS FOR CLEANING SUBMERGED SURFACES This invention relates to an apparatus for cleaning surfaces such as hulls of boats or walls of swimming pools submerged in a liquid such as water and more particularly to an apparatus having a conduit through which a pressurized stream of liquid flows to a nozzle of a jet pump which discharges a high velocity stream of water. A cleaning intake extends from the jet pump to adjacent the submerged surface and draws water across it to strip loose foreign material from the submerged surface.

In one prior art cleaning device of this kind for cleaning boat hulls, a wheel carriage is drawn along the submerged surface to carry a series of jet eductors across the surface being cleaned. The jet eductors are connected to an intake housing disposed adjacent the submerged surface to draw ambient water across the submerged surface and into the high velocity stream discharge from the jet eductors. The jet eductors are elbow shaped and by controlling the angles of the jet eductors relative to the submerged surface, a net reaction force or thrust may be provided for urging the device against the submerged surface.

Boats accumulate various loose marine growths and masses on their hulls which interfere with their racing speed. Thus, before a race or after a considerable period in the water, the submerged hulls are often cleaned either by divers or persons on the boat. Hulls, particularly of racing yachts or sailboats, have contoured surfaces which are difficult for a wheeled carriage to traverse particularly if the carriage must be held inwardly against the submerged surface while the carriage is being traversed. The manipulation of a cleaning device at the end of a long handle is particularly difficult when the boat hull curves inwardly and beneath the position of the operator of the cleaning apparatus on the boat deck. Also, the cleaning operation is more difficult where the cleaning device is heavy, large, or cumbersome.

' In accordance with the present invention, it has been found that sufficient laterally directed force may be established to hold the cleaning apparatus against the submerged surface while traversing the submerged surface and that a high velocity film of water may be caused to flow across the submerged surface to clean the same. These results have been achieved by having the low pressure intake to the jet pump across a resilient compressible pad which can conform to the contour of the submerged surface and maintain a thin wide film of high velocity flow across the inner surface of the pad while ambient pressure on the back of the large surface area of the pad forces the pad toward the submerged surface. More specifically, the high velocity film flow across the wide surface area at the inner side of the pad causes a pressure lower than the ambient pressure at the outer side of the pad; and the pressure differential therebetween results in a force applied to outer side urging the pad toward the submerged surface. By providing a lightweight construction for the cleaning apparatus, the force causing the cleaning apparatus to cling to the submerged surface overcomes the downward pull of gravity. Also, because the pad apparatus may be readily pushed or pulled without undue exertion.

Accordingly, a general object of the invention is to provide a new and improved cleaning apparatus for submerged surfaces of the foregoing kind.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of a cleaning apparatus embodying the novel features of the invention;

FIG. 2 is an enlargedcross-sectional view taken substantially along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged plan view of the apparatus of FIG. 1;

FIG. 4 is an enlarged fragmentary view of another embodiment of the invention having a cleaning brush; and I 1 FIG. 5 illustrates another embodiment of the invention having a filter attached to the outlet of the jet pump means.

As shown in the drawings for purposes of illustration, the invention is embodied in an apparatus 11 having a handle 12 and a conduit 14 within the handle and in fluid communication with a source of fluid under pressure such as water from a hose 15 attached to an upper end of the handle 12. The pressurized water flows downwardly in the conduit 14 to an inlet 16 of a jet pump means 17 and through a nozzle 18 therein from which issues a high velocity stream of liquid which then flows through an outlet 19 for discharge from the jet pump means 17. In accordance with Bernoulis theorem, the low pressure, high velocity stream of the jet pump will establish an area of low pressure which is communicated through an" intake passageway means 21 to some of the ambient water to cause the same to flow through the passageway means 21 to join the high velocity stream for flow from the pump outlet 19.

In accordance with the invention, the intake passageway means 21 extends to a pad means 27 to establish a less than ambient pressure across a wide inner wall or surface 29 of a compressible, resilient pad 30 to create a considerable holding force from a pressure differential between the inner surface 29 and an outer surface 33 of the pad means to urge the same against a submerged surface 34. More specifically, ambient pressure on an outer wide surface 33 of the pad means and a thin film high velocity liquid flowing across an inner surface 29 of the resilient pad 30 provide a pressure differential over a large area which generates sufficient force to urge the apparatus toward the submerged surface as it traverses it. As the compressible resilient pad 30 conforms closely to any varying contours and curves on the submerged surfaces, the spacing between the pad inner surface 29 and the submerged surface 34 is maintained quite small to provide a thin film but high velocity flow toward the central passageway means 21 and this high velocity flow acts to strip foreign material from the submerged surface. The pad 30 is preferably made of synthetic sponge material which is lightweight and readily glides on this liquid film when traversing the submerged surface. The pad 30, will, preferably, have a moderately rough surface so that it will normally be partially in direct contact with the submerged surface through surface asperities which project through the liquid film.

Additionally, as will be explained in greater detail, the preferred apparatus 11 is constructed substantially of lightweight materials such as plastics so that the laterally directed force from the pressure differential is able to overcome the force of gravity tending to pull the cleaning apparatus 11 downwardly along vertical submerged surfaces. Thus, it will be seen that a high velocity flow of liquid is attained across the inner surface of the pad 30 to strip and entrain marine growths and masses for flow into and through the passageway means 21 for discharge from the outlet 19 as the operator pushes or pulls the apparatus along the submerged surface.

Referring now in greater detail to the illustrated apparatus, as best seen in FIG. 1, the handle 12 may be formed with an upper section 36 and a lower section 37 which are connected together with a fluid tight fitting 38 to form a long handle. Preferably, the handle sections are preferably made from a lightweight aluminum alloy such as alloy 6063-T5. An upper end of the handle is provided with a fitting 39 for releasably attaching the handle to the hose which extends to a source of water under pressure such as a hose at a dock side or a garden or water hose at a pool side. Typically, water pressure from such source may vary from as low as 10 psi up to 60 psi, the illustrated apparatus works very well in this range but works extremely well with higher pressures, for example, 30 psi or greater. While the conduit 14 is within the hollow interior of the handle 12, other conduits such as separate hoses or pipes may be used with the handle.

To facilitate the cleaning of vertical surfaces underneath a person such as a boat hull, the lower end 41 of the lower handle section 37 is bent inwardly and is pivotally connected to a frame means 43 of the apparatus. More specifically, the pivotal connection between the handle 12 and the frame means is in the form of a yoke 45 secured to the bottom of the tubular handle and closing the lower end of its hollow interior. The yoke is formed with bifurcated arms 47 extending downwardly to adjacent the inside of a pair of upstanding flanges 48 of a U-shaped bracket 49 which has a central flat portion 50 between the flanges 48 fastened by fasteners 51, as best seen in FIGS. 2 and 3, to a portion of the frame means 43. Aligned apertures in the yoke arms 47 and in the upstanding flanges 48 receive pivot pins 53 which are aligned and define an axis about which the handle 12 may pivot relative to the frame means and the pad means 27. As best seen in FIGS. 1 and 3, a stop pin 54 may be carried by one of the flanges 4 8 to project inwardly into the path of tuming of a yoke arm 47 to limit the extent of turning of the handle in the counterclockwise direction, as viewed in FIG. 1.

To provide a rigid backing and support for the resilient pad 30, it is held within a pad holder 56 which includes a wide flat holder plate 55 covering the outer side of the pad. As seen in the drawings, it is preferred that the holder plate 55 have a relatively flat, wide surface area against which the ambient pressure may be applied to provide a relatively strong holding force for holding the apparatus against the submerged surface. The illustrated plate 55 has a pair of longitudinally extending reinforcing grooves 57 therein for providing increased rigidity and strength to the plate which is preferably made of a lightweight plastic such as polyvinyl chloride plastic. Preferably, the side edges of the holder plate 55 are integrally joined to downwardly turned flanges 59 on each of the four sides thereof to overlap partially vertically extending side walls 61 of the sponge pad 30 and thereby hold the pad 30 against shifting relative to the holder plate 55.

The sponge pad 30 is releasably secured to this holder plate 55 by means of a fastening means 63 in the form of thumb screw nuts screwed onto the upper ends of upwardly projecting screws having shanks projecting through aligned openings in the plate 55 and in an underlying backing plate 65 which is adhesively secured to the top of the resilient pad 30. When the resilient pad 30 is worn, the thumb screws may be unscrewed and the pad 30 with its attached backing 65 and projecting screws may be removed from the holder. A new sponge pad with its attached backing 65 and screws may be inserted into the pad holder and the wing nuts fastened to secure the new pad in place. The backing 65 may be a thin plastic sheet adhesively secured to the top of the resilient pad and may be substantially coextensive with its top surface.

The resilient pad 30 is rectangular in shape and is formed with a central cylindrical aperture or bore therein which serves as a portion of the passageway means 21 through which the foreign material removed from the submerged surface is carried to the jet pump means 17. To prevent the sponge about the bore 70 from bending and collapsing inwardly and closing off or restricting substantially the passageway means 21, a rigid sleeve 77 is inserted into the bore 70 and projects from the outer side of the sponge pad toward its inner surface 29. The illustrated sleeve 77 is three inches in diameter and made of polyvinyl chloride plastic. lntegrally formed on the upper end of the sleeve 77 is an outwardly directed flat flange 79 which is received in a space 81 between the underlying pad backing 65 and a raised central portion 83 of the backing plate 55. A plurality of fasteners 87 extend upwardly through aligned openings in the sleeve flange 79, in the backing plate 55 and in the central portion 50 of the U-shaped bracket 49 to secure these elements together.

The jet pump means 17 is disposed within the U- shaped bracket 49 and beneath the handle yoke 45 and in a position generally parallel to the holder plate 55. The inlet end of the jet pump means is connected to the conduit 14 in the handle 12 by a flexible hose 91 which permits swinging of the handle between various inclinations relative to the pump in the course of the cleaning operation. In this instance, the hose 91 is made of a lightweight plastic and is connected at its upper end to a nipple which is secured to and projects from the handle and which is in fluid communication with the conduit 14 within the handle. The lower end of the hose 91 is connected to a cylindrical sleeve 97 at the inlet 16 of the jet pump means 17.

The illustrated jet pump means 17 is of simple construction and includes a simple straight through jet 95 which includes the sleeve 97 in which is an internal cylindrical bore wall 99 defining the inlet 16 for the jet pump means. The jet 95 also includes a reduced diameter, coaxially aligned cylindrical bore wall 101 which defines a restricted orifice or nozzle 18 for the jet pump. Thus, liquid flowing through the inlet 16 into the nozzle 18 increases its velocity and leaves the nozzle 18 as a high velocity narrow stream flowing into the outlet 19 which includes a central section 105 of a Tee 107 which is standard polyvinyl chloride pipe fitting. By way of illustration only, illustrated jet-95 is made of metal with an internal diameter of 025 inch for the inlet 16 and an internal diameter of 0.180 inch for the nozzle 18. The illustrated jet 95 has an external thread 109 threaded into a bore of a collared reducing bushing 111. The reducing bushing 111 has a cylindrical outer wall 113 telescoped into a cylindrical opening of a section 115 of the Tee 107 and suitably fastened thereto as by an adhesive or by a force fit therebetween.

In a similar manner, an outlet section 117 of the Tee 107 receives an inserted end of a cylindrical discharge tube 119 having an internal cylindrical wall 121 defining a portion of the outlet 19 for directing liquid flow exiting the nozzle and the passageway means 21. Preferably, the pressurized liquid flowing into the jet eductor from conduit 14 partakes of a straight line flow from the inlet 16, through the nozzle and out of the outlet 18 to prevent clogging, additional turbulence or pressure drops which might cause clogging of the pump. To these ends, the longitudinal axis of the outlet tube 119 is coaxial with the longitudinal axis of the Tee sections 115 and 117 and also coaxial with the orifice 18 and inlet 16.

The Tee 107 also has a central section 120 which projects at right angles from the Tee sections 115 and 117. The Tee central section extends through a central opening 121 in the central portion 50 of the U-shaped bracket 49 and a central opening in the plate 55 and projects into the bore of the sleeve 77 for the resilient pad 30. In this instance, the central section 120 has an internal bore wall 125 and its outer wall is force fitted into a down-turned, annular flange 127 on the backing plate 55 of the pad holder. Thus, liquid and debris may flow through the sleeve 77 and the central Tee section 120 to join at substantially right angles the high velocity discharge from the nozzle 18 flowing through the Tee.

To assist the high velocity film of liquid in scrubbing the submerged surface 34, the apparatus may be provided, in accordance with another embodiment of the invention, with a brush means such as the brush 130 having bristles 131 for brushing against the submerged surface 34. The bristles are secured in a mounting block 133 which is adhered to an extension 65a of the backing plate for the sponge pad 30. The mounting block also is retained bya down-turned flange 590 which abuts an outer vertical wall 135 of the mounting block for the brush. A similar brush 130 may be provided at the other opposite end of the pad 30. Preferably, the bristles 131 project only slightly beyond the inner surface 29 of the pad 30 and do not interfere with its ability to be positioned closely adjacent the submerged surface 34. The sponge pad 30 and brush 130 are thus readily detachable and replaceable. Also, the foreign matter removed by the brush will be entrained by the high velocity film of water for flow through passageway means 21, as desired above.

When the apparatus is used for cleaning swimming pools or the like in which it is desired to filter the debris and foreign material such as leaves or other large articles from the water leaving the jet pump means 17, a filter means 140, asbest seen in FIG. 5, may be attached to a discharge end of the outlet tube 119. The illustrated filter means 140 includes a filter bag 141 which is sufficiently permeable to allow the water being discharged from the tube 119 to flow therethrough and impermeable to the passage of leaves and other foreign matter being cleaned from the submerged surface 34 of the pool. The filter bag is secured by means such as, for example, a ring clamp 143 clamping the open end of the filter bag about the discharge tube 119. With release of the clamp, the bag may be removed and then the foreign material may be removed from the filter bag. The filter bag 141 may also be attached to an apparatus having a brush such as the brush 130.

From the foregoing, it will be seen that the cleaning apparatus is simple, lightweight and economical in construction and clings to submerged surfaces because of the pressure differential established on opposite sides of a wide resilient pad movable along the submerged surface. With the present invention, a high velocity, very thin film of liquid between the inner face of the pad and the submerged surface provides a very good cleaning action; yet the cleaning apparatus glides easily on this thin film of liquid while traversing the submerged surface.

While a preferred embodiment has been shown and described, it will be understood that there is no intent to limit the invention by such disclosure but, rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. An apparatus for cleaning foreign material from a surface submerged in a liquid comprising, a frame means, conduit means for conveying a stream of liquid under pressure, a jet pump means having an inlet connected to said conduit means to receive said pressurized liquid and having a nozzle to increase the velocity of liquid flow, an outlet for said jet pump means for discharging liquid received from said nozzle, passageway means in fluid communication with said high velocity stream of liquid flow through said jet pump means and extending to a position adjacent the submerged surface, a pad means comprising a resilient, compressible pad having an inner surface for facing said submerged surface and for conforming thereto,

said passageway means leading to said inner surface of said pad means to provide a lower than ambient pressure at said inner surface to cause liquid to flow as a high velocity film in the space between said pad inner surface and the submerged surface, an outer surface on said pad means for exposure to said ambient pressure which will be at a pressure higher than the pressure within the high velocity film of liquid whereby a pressure differential will be created across said pad means to urge said pad toward said submerged surface, and means connected to frame means for traversing said pad for gliding along said submerged surface so that foreign material will be stripped from said submerged surface by said high velocity film of liquid as well as by partial contact with the resilient pad and be transported through said passageway means to said outlet for discharge with the high velocity flow from said nozzle.

2. An apparatus in accordance with claim 1 in which said pad means includes a replaceable pad of sponge material and a holder for releasably holding said pad and for allowing sponge pads to be replaced when worn.

3. An apparatus in accordance with claim 2 in which fastening means are provided for fastening said sponge pad to said holder.

4. An apparatus in accordance with claim 2 in which said sponge pad has an opening therein extending from said inner surface and said passageway means includes a sleeve attached to said holder and projecting into said opening in said sponge pad to a position adjacent the inner surface thereof to restrain the sponge material from flowing into and substantially restricting said passageway means.

5. An apparatus in accordance with claim 4 in which said passageway means includes a further sleeve in fluid communication with said outlet of said jet pump means and in telescoping relation with said sleeve of said holder whereby the high velocity film ofliquid will flow into said opening in said sponge pad and through said telescoped sleeves and through said outlet of said jet pump means.

6. An apparatus in accordance with claim 1 in which said jet pump means is a jet eductor secured to the outer side of said pad means for directing fluid flow along a path substantially parallel to said outer surface of said pad means.

7. An apparatus in accordance with claim 6 in which said means for transversing said pad comprises a hollow handle pivotally connected to said frame means and in which said conduit means comprises a hollow bore in the interior of said handle and a flexible hose extending between said handle bore and said inlet for said jet eductor.

8. An apparatus for cleaning foreign material from a surface submerged in a liquid comprising a frame means, a handle pivotally secured to said frame means for manipulation and for exerting a pushing and pulling force on said frame means to cause the same to traverse along said submerged surface, a conduit for receiving liquid under pressure, a jet eductor carried by said frame means with an inlet connected to said conduit to receive liquid under pressure, said jet eductor having a nozzle to cause an increase in velocity of the flow of liquid received from said inlet, an enlarged outlet for said jet eductor for receiving liquid from said nozzle, a compressible resilient pad carried by said frame means and having an inner flat surface for positioning adjacent the submerged surface, a passageway means extending from said jet eductor to a central location at said inner surface of said pad to establish a lower pressure than ambient pressure at said inner surface to cause ambient liquid to flow inwardly to said central location and in the space between said inner surface and said submerged surface, and means associated with the outer side of said pad providing an area for exposure to said ambient pressure and for establishing a pressure differential with the lower pressure and the liquid flowing between the inner surface of said pad and the submerged surface.

9. An apparatus in accordance with claim 8 in which a filter means is attached to said outlet of said jet eductor to filter foreign material from said liquid being discharged from said outlet.

10. An apparatus in accordance with claim 8 in which a brush means is carried by said frame means to extend to said submerged surface for assisting in cleaning and scrubbing foreign material from said submerged surface. 

1. An apparatus for cleaning foreign material from a surface submerged in a liquid comprising, a frame means, conduit means for conveying a stream of liquid under pressure, a jet pump means having an inlet connected to said conduit means to receive said pressurized liquid and having a nozzle to increase the velocity of liquid flow, an outlet for said jet pump means for discharging liquid received from said nozzle, passageway means in fluid communication with said high velocity stream of liquid flow through said jet pump means and extending to a position adjacent the submerged surface, a pad means comprising a resilient, compressible pad having an inner surface for facing said submerged surface and for conforming thereto, said passageway means leading to said inner surface of said pad means to provide a lower than ambient pressure at said inner surface to cause liquid to flow as a high velocity film in the space between said pad inner surface and the submerged surface, an outer surface on said pad means for exposure to said ambient pressure which will be at a pressure higher than the pressure within the high velocity film of liquid whereby a pressure differential will be created across said pad means to urge said pad toward said submerged surface, and means connected to frame means for traversing said pad for gliding along said submerged surface so that foreign material will be stripped from said submerged surface by said high velocity film of liquid as well as by partial contact with the resilient pad and be transported through said passageway means to said outlet for discharge with the high velocity flow from said nozzle.
 2. An apparatus in accordance with claim 1 in which said pad means includes a replaceable pad of sponge material and a holder for releasably holding said pad and for allowing sponge pads to be replaced when worn.
 3. An apparatus in accordance with claim 2 in which fastening means are provided for fastening said sponge pad to said holder.
 4. An apparatus in accordance with claim 2 in which said sponge pad has an opening therein extending from said inner surface and said passageway means includes a sleeve attached to said holder and projecting into said opening in said sponge pad to a position adjacent the inner surface thereof to restrain the sponge material from flowing into and substantially restricting said passageway means.
 5. An apparatus in accordance with claim 4 in which said passageway means includes a further sleeve in fluid communication with said outlet of said jet pump means and in telescoping relation with said sleeve of said holder whereby the high velocity film of liquid will flow into said opening in said sponge pad and through said telescoped sleeves and through said outlet of said jet pump means.
 6. An apparatus in accordance with claim 1 in which said jet pump means is a jet eductor secured to the outer side of said pad means for directing fluid flow along a path substantially parallel to said outer surface of said pad means.
 7. An apparatus in accordance with claim 6 in which said means for transversing said pad comprises a hollow handle pivotally connected to said frame means and in which said conduit means comprises a hollow bore in the interior of said handle and a flexible hose extending between said handle bore and said inlet for said jet eductor.
 8. An apparatus for cleaning foreign material from a surface submerged in a liquid comprising a frame means, a handle pivotally secured to said frame means for manipulation and for exerting a pushing and pulling force on said frame means to cause the same to traverse along said submerged surface, a conduit for receiving liquid under pressure, a jet eductor carried by said Frame means with an inlet connected to said conduit to receive liquid under pressure, said jet eductor having a nozzle to cause an increase in velocity of the flow of liquid received from said inlet, an enlarged outlet for said jet eductor for receiving liquid from said nozzle, a compressible resilient pad carried by said frame means and having an inner flat surface for positioning adjacent the submerged surface, a passageway means extending from said jet eductor to a central location at said inner surface of said pad to establish a lower pressure than ambient pressure at said inner surface to cause ambient liquid to flow inwardly to said central location and in the space between said inner surface and said submerged surface, and means associated with the outer side of said pad providing an area for exposure to said ambient pressure and for establishing a pressure differential with the lower pressure and the liquid flowing between the inner surface of said pad and the submerged surface.
 9. An apparatus in accordance with claim 8 in which a filter means is attached to said outlet of said jet eductor to filter foreign material from said liquid being discharged from said outlet.
 10. An apparatus in accordance with claim 8 in which a brush means is carried by said frame means to extend to said submerged surface for assisting in cleaning and scrubbing foreign material from said submerged surface. 